strapless

nouns

a woman's garment that exposes the shoulders and has no shoulder straps
strapless
is a type of (narrower)
a one-piece garment for a woman; has skirt and bodice
dress, frock

adjectives

having no straps
"a strapless evening gown"
strapless
is similar to
not held up or borne
"removal of the central post left the roof unsupported"
unsupported